US8625309B2 - Semiconductor integrated circuit and switching power supply system - Google Patents

Semiconductor integrated circuit and switching power supply system Download PDF

Info

Publication number
US8625309B2
US8625309B2 US13/178,909 US201113178909A US8625309B2 US 8625309 B2 US8625309 B2 US 8625309B2 US 201113178909 A US201113178909 A US 201113178909A US 8625309 B2 US8625309 B2 US 8625309B2
Authority
US
United States
Prior art keywords
voltage
semiconductor switch
signal
power supply
turned
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active, expires
Application number
US13/178,909
Other languages
English (en)
Other versions
US20120008346A1 (en
Inventor
Kazuhiro Kawamura
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Fuji Electric Co Ltd
Original Assignee
Fuji Electric Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Fuji Electric Co Ltd filed Critical Fuji Electric Co Ltd
Assigned to FUJI ELECTRIC CO., LTD. reassignment FUJI ELECTRIC CO., LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: KAWAMURA, KAZUHIRO
Publication of US20120008346A1 publication Critical patent/US20120008346A1/en
Application granted granted Critical
Publication of US8625309B2 publication Critical patent/US8625309B2/en
Active legal-status Critical Current
Adjusted expiration legal-status Critical

Links

Images

Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33507—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters
    • H02M3/33523—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters with galvanic isolation between input and output of both the power stage and the feedback loop

Definitions

  • Embodiments of the present invention relate semiconductor integrated circuits and particularly to semiconductor integrated circuits for carrying out stabilization of an output voltage of an insulating transformer.
  • a switching power supply system is mounted on an electronic device such as, for example, a cellular phone or a digital camera to be used for stepping up or stepping down an input voltage to be supplied to a load.
  • states relating to the operations of a power supply are set with various methods according to power supply specifications required by electronic devices.
  • a switching frequency with respect to a switching power supply system affect characteristics of the system such as a power supply noise characteristic, dimensions of parts, breakdown voltages of parts and temperature rise of parts, so that there are some ideas of methods of setting such important parameters.
  • a DC voltage supplied from a DC power supply is stepped up to be supplied to six white light emitting diodes connected in series as a load so as to drive the white light emitting diodes.
  • an external resistor as an adjusting resistor is provided for the oscillating circuit of a step up chopper regulator.
  • a switching power supply circuit When a switching power supply circuit is normally used for electronic equipment such as a portable appliance, a liquid crystal television set or a DVD (Digital Versatile Disc) player, noises generated from the switching power supply circuit may be classified into noises having adverse effects on other integrated circuits in the electronic equipment and noises having no adverse effects.
  • the invention of the switching power supply circuit disclosed in JP-A-2007-14082 since the resistance value of the external resistor and the switching period are in a linear relation to each other, is formed so that the switching period is freely varied by replacing one external resistor to facilitate adjustment of produced noises.
  • a power supply control IC Integrated Circuit
  • step up chopper regulator there is left such a problem as to require a specialized terminal for newly connecting a frequency adjusting resistor to the IC.
  • a power supply control IC for controlling a switching power supply system has the number of terminals come to be limited due to requirements for reductions in cost and in the package area. Therefore, in many cases, power supply control ICs have no specialized terminal provided for setting parameters other than the above explained switching frequency. In such case, for complying with various power supply specifications of electronic equipment, the lineup of power supply control ICs themselves must be made increased.
  • JP-A-2007-73954 As a system addressing such requirement, in JP-A-2007-73954 (see paragraph Nos. [0003] to [0028], etc.), a system is disclosed which system carries out the setting of an operating state during the initialization period of a power supply control IC without increasing the number of terminals of the power supply control IC.
  • the described system for carrying out selection of a required functional parameter and a required operation mode from a plurality of functional parameters and operation modes, is to actualize settings of a plurality of operating states with a single component by, for example, selecting a specified capacitance value of capacitance values of a multifunctional capacitor coupled to a pin of an integrated circuit.
  • a multifunctional capacitor is a capacitor which has, in addition to functions of setting in the initialization period functional parameters, operation modes or other device characteristics of the integrated circuit to which the multifunctional capacitor is connected, normal functions of some kinds for the normal operation of the integrated circuit.
  • a capacitor such as a power supply pin decoupling capacitor or a feedback pin loop compensating capacitor can be used as a parameter/mode selection capacitor during initialization.
  • the feedback pin loop compensating capacitor has its original purpose to compensate the frequency characteristic of the feedback pin loop of a power supply control IC and is to be disposed so that no feedback loop for a power supply control in a switching power supply system becomes unstable.
  • the feedback pin loop compensating capacitor with its capacitance value set to be less than the value optimum for the stability of the feedback loop, causes the system to be unstable to oscillate. Conversely, the capacitance value set to be more than the optimum value causes the response as a power supply system to become slow, which makes the output voltage impossible to recover soon to the variation of a load, for example.
  • the capacitance value of the capacitor significantly affects the response of a feedback system to be a problem of restricting the design itself of a switching power supply in that the change in the capacitance value limits the adjustment of phase compensation and causes an abnormal oscillation of the power supply.
  • a first case is the case in which like in the case disclosed in JP-A-2007-73954, a power supply voltage is supplied from an external power supply connected to different terminals of the power supply control IC to be produced as a power supply voltage by an internal regulator.
  • a second case is the case in which in an initialization period at startup, a power supply voltage is produced by a startup current produced by a startup circuit (corresponding to the internal regulator in the first case) connected to an external power supply and, in a normal operation, a power supply voltage is supplied from the auxiliary winding of an insulating transformer.
  • a third case is the case in which an external power supply is used.
  • the power supply pin decoupling capacitor is a capacitor to be connected to a power supply pin (between a power supply pin and a ground pin) of the power supply control IC for supplying a power supply voltage to the power supply control IC itself.
  • the power supply pin decoupling capacitor is a capacitor that functions as a buffer when power consumption of the power supply control IC becomes high to cause the supply of power supply voltage to become insufficient or to cause the power supply voltage to vary.
  • the power supply pin decoupling capacitor also functions for removing noises such as ripples in a voltage on an electric power supply line.
  • the capacitance value of the power supply pin decoupling capacitor must be made large to some extent.
  • the value of the constant current supplied from the regulator must be set large, which requires the use of a large-scale regulator for generating a large constant current. Therefore, the use of a multifunctional capacitor causes a problem with respect to cost.
  • a power supply voltage is supplied to the power supply control IC with power supply pins connected to an external power supply, so that the power supply pin decoupling capacitor is brought into a state of being always connected to the external power supply.
  • the power supply pin decoupling capacitor is charged by a constant current in such a state of connection, no distinction is possible as to whether the power supply pin decoupling capacitor is charged by the current from the external power supply or charged by the constant current produced in the power supply control IC. Namely, for using the power supply pin decoupling capacitor for mode setting in an initialization period, the power supply pins must be disconnected from the external power supply and a circuit for the disconnection is to be provided out of the power supply control IC.
  • the method disclosed in JP-A-2007-73954 can be said to be inadequate for being applied to the third case to set parameter/mode.
  • JP-A-2007-258294 see paragraph Nos. [0023] to [0027], etc.
  • a semiconductor integrated circuit which is provided so that a mode switching signal is made inputted without increasing the number of terminals.
  • terminals necessary for a normal operation a terminal is used to which a voltage is inputted whose voltage range in a normal operation has significant differences between a power supply voltage and between a ground voltage.
  • a voltage near the power supply voltage or near the ground voltage is inputted to the terminal so that a mode switching of the semiconductor integrated circuit is carried out. Therefore, according to the technique disclosed in JP-A-2007-258294, a semiconductor integrated circuit can be provided to which a mode switching signal can be inputted without increasing the number of terminals.
  • the circuit disclosed in the application is a circuit in which a resistor for making a decision with respect to a state is added to a terminal for outputting a control signal or a terminal for inputting a sensing current signal. At the rising of a power supply voltage, the resistance value is read in so as to set an operation mode according to the magnitude of the resistance value. The circuit, however, is operated on condition that the mode setting is carried out in the early stage, so that the circuit does not permit a mode change during operation.
  • the circuit disclosed in JP-A-2002-136124 is a circuit in which the output of a control winding (auxiliary winding) for detecting the output voltage of a secondary output winding of a transformer is made to be pulled down by a photocoupler to thereby give instructions for a mode change to a control unit.
  • a control winding auxiliary winding
  • this is to require a specialized terminal receiving the output of the control winding.
  • an auxiliary winding is generally used first for supplying a power supply voltage to a power supply control IC forming a control unit.
  • FIG. 4 is a circuit diagram showing an example of a configuration of a circuit of a related switching power supply system
  • FIG. 5 is a waveform diagram showing operation waveforms of basic parts of the related switching power supply system.
  • the switching power supply system shown in FIG. 4 is a switching power supply carrying out switching using self-excited oscillation and having a transformer T, a semiconductor switch Q 1 , a control IC 100 and a feedback circuit 11 .
  • the transformer T has a primary winding N 1 , a secondary winding N 2 and an auxiliary winding N 3 .
  • a DC power supply 12 is connected to one end of the primary winding N 1 of the transformer T.
  • the other end of the primary winding N 1 of the transformer T is grounded through the semiconductor switch Q 1 and a resistor R 1 for current detection.
  • the secondary winding N 2 of the transformer T is connected to output terminals 13 through a rectifying and smoothing circuit with a diode D 1 and an output capacitor C 1 .
  • the semiconductor switch Q 1 is to be an N channel MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) here.
  • the drain of the semiconductor switch Q 1 is connected to the primary winding N 1 of the transformer T, the source is connected to the resistor R 1 and the gate is connected to a control and output terminal OUT of the control IC 100 .
  • auxiliary winding N 3 of the transformer T is connected to a zero current detecting terminal ZCD of the control IC 100 and to a power supply terminal VCC of the control IC 100 through a diode D 2 .
  • the other end of the auxiliary winding N 3 is grounded.
  • the feedback circuit 11 To the output terminal 13 on the positive polarity side of the switching power supply system, the feedback circuit 11 is connected.
  • the feedback circuit 11 has resistors R 2 and R 3 both detecting variation of the output voltage at the output terminals 13 , a shunt regulator 14 , a photocoupler PC 1 including a light-emitting side photocoupler element PC 1 e and a photo-detecting side photocoupler element PC 1 r , and a resistor R 4 for limiting a current.
  • the photo-detecting side photocoupler element PC 1 r is connected to a feedback terminal FB in the control IC 100 with the collector and is grounded with the emitter.
  • the shunt regulator 14 let a current, corresponding to the variation in an output voltage detected by the resistors R 2 and R 3 , flow in the light-emitting side photocoupler element PC 1 e and, by the photo-detecting side photocoupler element PC 1 r , an error signal corresponding to the variation is inputted to the feedback terminal FB in the control IC 100 .
  • the control IC 100 makes the semiconductor switch Q 1 turned-off, no current flows in the resistor R 1 , by which the level of the signal inputted to a current detecting terminal IS is made to be zero.
  • a signal making the semiconductor switch Q 1 turned-on is outputted from a control output terminal OUT, the semiconductor switch Q 1 is made turned-on.
  • This makes a current flow in the primary winding N 1 of the transformer T and the semiconductor switch Q 1 to make electromagnetic energy stored in the primary winding N 1 .
  • the electromagnetic energy stored in the period is, during the period in which the semiconductor switch Q 1 is made turned-off, released from the secondary winding N 2 to the output capacitor C 1 through the diode D 1 .
  • the output voltage of the switching power supply system is easily affected by variations in the input voltage from the DC power supply 12 and in load.
  • the feedback circuit 11 carries out feedback of a voltage corresponding to an error to the specified output voltage to the control IC 100 as a feedback signal.
  • a duty as a period during which the semiconductor switch Q 1 is turned-on is controlled, by which an operation for stabilizing the output voltage is carried out.
  • the timing at which the state of the semiconductor switch Q 1 is changed from a turned-on state to a turned-off state becomes the time at which a (feedback terminal voltage)/n (n: a certain value), a voltage to which a feedback terminal voltage at the feedback terminal FB is reduced to 1/n (or a voltage to which the feedback terminal voltage is level shifted to 1/n), and a voltage at the current detecting terminal IS becomes equal to each other.
  • the timing at which the semiconductor switch Q 1 is turned-on is the time at which the detected voltage at the zero current detecting terminal ZCD comes closer to zero.
  • the semiconductor switch Q 1 when the semiconductor switch Q 1 is turned-off to allow electromagnetic energy stored in the primary winding N 1 to be released to the output side through the secondary winding N 2 , the voltage across the secondary winding N 2 and the voltage across the primary winding N 1 are decreased. This state is also transmitted to the auxiliary winding N 3 .
  • the semiconductor switch Q 1 when the voltage across the auxiliary winding N 3 is made inputted to the zero current detecting terminal ZCD to detect that the detected voltage comes closer to zero, the semiconductor switch Q 1 is made turned-on.
  • the zero current detecting terminal ZCD is a terminal for detecting the timing at which the semiconductor switch Q 1 is to be turned-on.
  • the voltage at the feedback terminal FB comes to increase. Then, the turned-on period of the semiconductor switch Q 1 until the feedback terminal voltage/n coincides with the voltage at the current detecting terminal IS (or a voltage to which the feedback terminal voltage/n is level-shifted) becomes longer to increase an amount of the energy stored in the primary winding N 1 , which acts so as to increase the output voltage.
  • the switching power supply system is provided with a mode switching circuit 15 .
  • the mode switching circuit 15 has a mode switching signal input terminal 16 , which is connected to the base of a transistor Q 2 through a resistor R 5 . Between the base and emitter of the transistor Q 2 , a resistor R 6 is connected and the emitter of the transistor Q 2 is grounded.
  • the collector of the transistor Q 2 is connected to the output terminal 13 on the positive polarity side of the switching power supply system through a light-emitting side photocoupler element PC 2 e of a photocoupler PC 2 , including the light-emitting side photocoupler element PC 2 e and a photo-detecting side photocoupler element PC 2 r , and a resistor R 7 .
  • the collector of the photo-detecting side photocoupler element PC 2 r is connected to a switching signal detecting terminal MC and is further connected to the power supply terminal VCC of the control IC 100 through a pull-up resistor R 8 .
  • the emitter of the photo-detecting side photocoupler element PC 2 r is grounded.
  • the transistor Q 2 With a mode switching signal inputted to the mode switching signal input terminal 16 being at an H (High) level, the transistor Q 2 is made turned-on to bring the light-emitting side photocoupler element PC 2 e to emit light. This makes the photo-detecting side photocoupler element PC 2 r turned-on to bring the electric potential of the switching signal detecting terminal MC to an L (Low) level. Moreover, with the mode switching signal being at an L level, the transistor Q 2 is made turned-off to cause the light-emitting side photocoupler element PC 2 e to emit no light. This turns-off the photo-detecting side photocoupler element PC 2 r to bring the electric potential of the switching signal detecting terminal MC to become the H level.
  • the control IC 100 carries out switching of a mode depending on whether the electric potential of the switching signal detecting terminal MC is the L level or the H level.
  • the switching signal detecting terminal MC was independently provided in the control IC 100 .
  • the photocoupler PC 2 including the light-emitting side photocoupler element PC 2 e and the photo-detecting side photocoupler element PC 2 r were used.
  • a mode switching signal was externally inputted to change the logic state at the switching signal detecting terminal MC and the change was detected by the inner circuit of the control IC 100 , by which switching to a specified operation was carried out.
  • a specialized terminal must be provided in the control IC.
  • a current standard control IC for a switching power supply for AC to DC conversion or DC to DC conversion is provided with eight pins (terminals). The minimum kinds of necessary functions are incorporated so as to be exhibited through the eight pins. Therefore, when no free pins are provided for new functions, some of present convenient functions must be eliminated for providing the new functions or, in the worst case, the package must be changed for increasing the number of pins. This causes the control IC to be insufficient in functions or to be provided at increased cost.
  • the invention was made in view of such points with an object of providing a semiconductor integrated circuit that can detect an externally inputted mode switching signal without newly providing any specialized terminal, and a switching power supply system provided with such a semiconductor integrated circuit.
  • a semiconductor integrated circuit which is a semiconductor integrated circuit including: a control output terminal which outputs a signal driving a semiconductor switch connected to a primary winding of a transformer; a current detecting terminal to which a first voltage signal is inputted to which signal a current flowing in the semiconductor switch is converted; a feedback terminal to which a voltage corresponding to an error of a secondary side output voltage of the transformer is fed back; and a zero current detecting terminal which is connected to an auxiliary winding of the transformer for detecting from the output voltage of the auxiliary winding of the transformer one of a timing at which the semiconductor switch is to be turned-on and both of the timing at which the semiconductor switch is to be turned-on and a timing at which the semiconductor switch is turned off, the semiconductor integrated circuit including: a timer which outputs a signal after a specified length of time from the timing at which the semiconductor switch is made turned-off; a comparator which is connected to the current detecting terminal to detect a second
  • a switching power supply system which is a switching power supply system including: a transformer which has a primary winding, a secondary winding and an auxiliary winding; a semiconductor switch connected to the primary winding; a feedback circuit which carries out feedback of a voltage corresponding to an error of an output voltage outputted from the secondary winding; and a semiconductor integrated circuit including: a current detecting terminal to which a first voltage signal is inputted to which signal a current flowing in the semiconductor switch is converted; a feedback terminal to which a voltage corresponding to an error of the output voltage fed back by the feedback circuit is inputted; and a zero current detecting terminal which is connected to the auxiliary winding for detecting from the output voltage of the auxiliary winding one of a timing at which the semiconductor switch is to be turned-on and both of the timing at which the semiconductor switch is to be turned-on and a timing at which the semiconductor switch is turned-off, the semiconductor switch being controlled so as to stabilize the output voltage by the first voltage signal and the voltage corresponding
  • the semiconductor integrated circuit can be provided with the timer, the comparator and the operation mode switching unit.
  • the timer allowing the comparator so as to detect the second voltage signal after a specified length of time has passed from the turning-off of the semiconductor switch, the switching between different operation modes by the operation mode switching unit is made possible without newly providing any specialized terminal.
  • the current detecting terminal in the semiconductor integrated circuit functions so that, in addition to making the first voltage signal in a normal operation inputted in a period in which the semiconductor switch is made turned-on, the second voltage signal based on an externally inputted mode switching signal can be also detected in a period in which the semiconductor switch is made turned-off.
  • the second voltage signal detectable which is normally considered not to appear at the current detecting terminal in a period in which the semiconductor switch is made turned-off, there is provided the advantage of making a specified mode switching become possible without newly providing an additional specialized terminal for detecting an external signal or without carrying out omission of an existing useful function which omission is for additionally providing an external signal detecting function.
  • FIG. 1 is a circuit diagram showing an example of a configuration of a circuit of a switching power supply system according to a first embodiment of the invention
  • FIG. 2 is a waveform diagram showing operation waveforms of basic parts of the switching power supply system according to the first embodiment of the invention
  • FIG. 3 is a circuit diagram showing an example of a configuration of a circuit of a switching power supply system according to a second embodiment of the invention
  • FIG. 4 is a circuit diagram showing an example of a configuration of a circuit of a related switching power supply system.
  • FIG. 5 is a waveform diagram showing operation waveforms of basic parts of the related switching power supply system.
  • FIG. 1 is a circuit diagram showing an example of a configuration of a circuit of a switching power supply system according to a first embodiment of the invention and FIG. 2 is a waveform diagram showing operation waveforms of basic parts of the switching power supply system.
  • constituents having the same functions as those of the constituents in the example of the circuit configuration of the related switching power supply system shown in FIG. 4 are denoted with the same reference numerals and signs.
  • the switching power supply system has a transformer T, a semiconductor switch Q 1 , a control IC 10 and a feedback circuit 11 .
  • the transformer T has a primary winding N 1 , a secondary winding N 2 and an auxiliary winding N 3 .
  • a DC power supply 12 is connected to one end of the primary winding N 1 of the transformer T.
  • the DC power supply 12 can be a power supply in which the output of a commercial AC power supply is subjected to a full-wave rectification by a diode bridge.
  • the other end of the primary winding N 1 of the transformer T is grounded through the semiconductor switch Q 1 and a resistor R 1 for current detection.
  • the secondary winding N 2 of the transformer T is connected to output terminals 13 through a rectifying and smoothing circuit with a diode D 1 and an output capacitor C 1 .
  • the semiconductor switch Q 1 is to be an N channel MOSFET here.
  • the drain of the semiconductor switch Q 1 is connected to the primary winding N 1 of the transformer T, the source is connected to the resistor R 1 and a current detecting terminal IS of the control IC 10 , and the gate is connected to a control and output terminal OUT of the control IC 10 .
  • a capacitor Cd for resonance is connected between the drain and the source of the semiconductor switch Q 1 .
  • One end of the auxiliary winding N 3 of the transformer T is connected to a power supply terminal VCC of the control IC 10 through a diode D 2 and, along with this, connected to a zero current detecting terminal ZCD of the control IC 10 .
  • the feedback circuit 11 To the output terminal 13 on the positive polarity side of the switching power supply system, the feedback circuit 11 is connected.
  • the feedback circuit 11 has resistors R 2 and R 3 connected in series both of which are connected between the output terminal 13 on the positive polarity side and the ground on the secondary side to detect variation of the output voltage at the output terminals 13 .
  • a resistor R 4 for limiting a current, a light-emitting side photocoupler element PC 1 e of a photocoupler PC 1 and a shunt regulator 14 are connected in series.
  • the connection section common to the resistor R 2 and the resistor R 3 To the reference terminal of the shunt regulator 14 , the connection section common to the resistor R 2 and the resistor R 3 is connected.
  • a photo-detecting side photocoupler element PC 1 r paired with the light-emitting side photocoupler element PC 1 e is connected to a feedback terminal FB in the control IC 10 with the collector and is grounded with the emitter.
  • the shunt regulator 14 let a current, corresponding to the variation in an output voltage detected by the resistors R 2 and R 3 , flow in the light-emitting side photocoupler element PC 1 e and, by the photo-detecting side photocoupler element PC 1 r , an error signal corresponding to the variation is inputted to the feedback terminal FB in the control IC 10 .
  • a current mode control type switching power supply is formed in which the value of a voltage to which a current flowing in the semiconductor switch Q 1 is converted and the value of a fed back voltage corresponding to an error in the output voltage are compared with each other to thereby carry out control of stabilizing the output voltage.
  • the switching power supply system is further provided with mode switching circuits 15 a and 15 b .
  • the mode switching circuit 15 a has a mode switching signal input terminal 16 to which a mode switching signal is inputted.
  • the mode switching signal input terminal 16 is connected to the base of an NPN-type transistor Q 2 through a resistor R 5 .
  • the base of the transistor Q 2 is connected to one end of a resistor R 6 , and the other end of the resistor R 6 and the emitter of the transistor Q 2 are connected to the ground on the secondary side.
  • the collector of the transistor Q 2 is connected to the output terminal 13 on the positive polarity side of the switching power supply system through a light-emitting side photocoupler element PC 2 e of a photocoupler PC 2 , including the light-emitting side photocoupler element PC 2 e and a photo-detecting side photocoupler element PC 2 r , and a resistor R 7 .
  • a diode D 3 between one end of the auxiliary winding N 3 connected to the zero current detecting terminal ZCD of the control IC 10 and the current detecting terminal IS, there are connected a diode D 3 , a resistor R 9 for level adjustment and a PNP type transistor Q 3 are connected in series. Between the emitter and the base of the transistor Q 3 , a resistor R 10 is connected. The base of the transistor Q 3 is connected to the ground through a resistor R 11 . Moreover, to a connection point A of the emitter of the transistor Q 3 and the resistor R 9 for level adjustment, a photo-detecting side photocoupler element PC 2 r is connected which is paired with the light-emitting side photocoupler element PC 2 e.
  • the control IC 10 has the power supply terminal VCC and a ground terminal GND.
  • the power supply terminal VCC has a power supply voltage supplied from the auxiliary winding N 3 and the ground terminal GND is connected to the ground on the primary side.
  • the control IC 10 further has a comparator CP 1 to the non-inverting input terminal of which the zero current detecting terminal ZCD is connected.
  • a voltage source VP 1 is connected to the inverting input terminal of the comparator CP 1 .
  • a threshold voltage as a threshold level is set which is lower than a voltage appearing in the auxiliary winding N 3 when the semiconductor switch Q 1 is made turned-off.
  • a timer 21 is connected to the output terminal of the comparator CP 1 .
  • the timer 21 has a function that starts its operation from a timing at which the comparator CP 1 detects the turning-off of the semiconductor switch Q 1 and, after a specified time has passed, outputs a pulse signal.
  • the zero current detecting terminal ZCD is also connected to the set terminal S of an RS flip-flop circuit 24 through a valley detecting unit 22 and a one-shot circuit 23 .
  • the output terminal Q of the RS flip-flop circuit 24 is connected to the control output terminal OUT of the control IC 10 through a driver 25 .
  • the feedback terminal FB of the control IC 10 is connected to the inverting input terminal of a current comparator 27 through a level shift circuit 26 .
  • the output terminal of the current comparator 27 is connected to the reset terminal R of the RS flip-flop circuit 24 .
  • the current detecting terminal IS of the control IC 10 is connected to the non-inverting input terminal of the current comparator 27 and the non-inverting input terminal of a comparator CP 2 .
  • a voltage source VP 2 is connected to the inverting input terminal of the comparator CP 2 .
  • a threshold voltage is set which is lower than a voltage appearing in the auxiliary winding N 3 when the semiconductor switch Q 1 is made turned-off and applied to the current detecting terminal IS through the diode D 3 , the resistor R 9 and the transistor Q 3 of the mode switching circuit 15 b.
  • the output terminal of the comparator CP 2 is connected to the data input terminal D of a D (delayed) flip-flop circuit 28 , to the clock input terminal CK of which the timer 21 , outputting a pulse signal, is connected.
  • the output terminal Q of the D flip-flop circuit 28 is connected to an overcurrent limiting threshold voltage changing circuit 29 .
  • the overcurrent limiting threshold voltage changing circuit 29 is shown as an example of an operation mode switching unit that switches an operation mode when a mode switching signal is externally inputted to the mode switching signal input terminal 16 .
  • the overcurrent limiting threshold voltage changing circuit 29 is provided with two voltage sources VP 3 and VP 4 , which are connected to an inverting input terminal of the current comparator 27 through a switch SW 1 and a switch SW 2 , respectively.
  • the switch SW 1 is driven to be turned-on and -off by an inverter 30 receiving the output of the D flip-flop circuit 28 and the switch SW 2 is driven to be turned-on and -off by the output of the D flip-flop circuit 28 .
  • the turning-on of the semiconductor switch Q 1 with an H level signal received from the control output terminal OUT makes a current flow in the primary winding N 1 of the transformer T to store electromagnetic energy in the primary winding N 1 .
  • the value of the current flowing in the primary winding N 1 is converted to the value of a voltage by the resistor R 1 to be inputted to the current detecting terminal IS.
  • a negative voltage is generated the value of which is expressed as the value of an input voltage ⁇ the number of turns of the auxiliary winding N 3 /the number of turns of the primary winding N 1 .
  • the turning-off of the semiconductor switch Q 1 allows the electromagnetic energy stored in the primary winding N 1 of the transformer T to be released from the secondary winding N 2 to the output capacitor C 1 through the diode D 1 .
  • a positive voltage is generated in the auxiliary winding N 3 with magnitude becoming Vs ⁇ (the number of turns of the auxiliary winding N 3 )/(the number of turns of the secondary winding N 2 ).
  • the voltage is rectified by the diode D 2 and supplied to the power supply terminal VCC of the control IC 10 to be used as a power supply voltage of the control IC 10 .
  • the drain voltage of the semiconductor switch Q 1 is rapidly lowered due to the resonance in the circuit with the primary winding N 1 and the capacitor Cd with a voltage induced in the auxiliary winding N 3 also lowered.
  • the voltage induced in the auxiliary winding N 3 is also inputted to the zero current detecting terminal ZCD.
  • the one-shot circuit 23 outputs a set signal, which is inputted to the RS flip-flop circuit 24 to turn-on the semiconductor switch Q 1 again.
  • the transistor Q 2 in the mode switching circuit 15 a comes to be in a turned-on state to make an LED as the light-emitting side photocoupler element PC 2 e turned-on (emit light).
  • the transistor Q 3 is reverse-biased to thereby be turned-off, by which the voltage of the auxiliary winding N 3 does not exert any influence on the voltage at the current detecting terminal IS.
  • the current detecting terminal IS like in the circuit of the related system, a voltage with a triangular waveform to which a current is converted into a voltage is generated only when the semiconductor switch Q 1 is made turned-on.
  • the operation mode is the A mode
  • no high positive voltage which appears in the auxiliary winding N 3 when the semiconductor switch Q 1 is made turned-off
  • the comparator CP 2 always outputs an L level signal.
  • the comparator CP 1 detects a high positive voltage supplied from the auxiliary winding N 3 each time the semiconductor switch Q 1 is turned-off and the timer 21 outputs a pulse signal a specified time later from the instant when the high positive voltage is detected.
  • the D flip-flop circuit 28 at the time when the D flip-flop circuit 28 receives a pulse signal from the timer 21 at the clock input terminal CK, holds the L level signal outputted from the comparator CP 2 and outputs the L level signal from the output terminal Q until the clock input terminal CK receives a next pulse signal.
  • the switch SW 1 is in a turned-on state (closed: in conduction state) by receiving an H level signal, to which the L level signal outputted from the output terminal Q of the D flip-flop circuit 28 is inverted by the inverter 30 , to supply the voltage of the voltage source VP 3 to the current comparator 27 as an overcurrent limiting threshold voltage.
  • the switch SW 2 directly receives the L level signal to be in a turned-off state (opened: shut off state).
  • the transistor Q 2 is turned-off to make the LED as the light-emitting side photocoupler element PC 2 e turned-off (emit no light). This is to cause the phototransistor as the photo-detecting side photocoupler element PC 2 r in the mode switching circuit 15 b to be made turned-off.
  • the transistor Q 3 is made turned-on to come to supply the generated positive voltage to the current detecting terminal IS.
  • the voltage across the auxiliary winding N 3 becomes a negative voltage. Therefore, without taking any measures, the voltage at the current detecting terminal IS is pulled down to the negative side to make it impossible to carry out proper comparison of the voltage at the current detecting terminal IS with a feedback signal voltage. It is the diode D 3 that is provided for avoiding this. The diode D 3 prevents the voltage at the current detecting terminal IS from being pulled down onto the negative voltage side.
  • the resistor R 1 comes to have no current flowing therein from the primary winding N 1 of the transformer T through the semiconductor switch Q 1 but have instead a current flowing from the auxiliary winding N 3 due to a voltage generated in the auxiliary winding N 3 , by which the voltage at the current detecting terminal IS is pulled up onto the positive polarity side.
  • the resistor R 9 for voltage level adjustment the voltage value at the current detecting terminal IS can be adjusted.
  • the resistance value of the resistor R 9 for the voltage level adjustment is selected so that the voltage at the current detecting terminal IS becomes on the order of 1V.
  • the comparator CP 1 compares the value of the voltage at the zero current detecting terminal ZCD with the threshold voltage set by the voltage source VP 1 to detect the timing at which the semiconductor switch Q 1 is made turned-off. While, the comparator CP 2 compares the voltage at the current detecting terminal IS with the threshold voltage set by the voltage source VP 2 to detect a voltage to be supplied during the period in which the semiconductor switch Q 1 is made turned-off.
  • the timer 21 is a device for making the operation of the D flip-flop circuit 28 so as not to be affected by the distortion in the voltage waveform at the current detecting terminal IS due to a noise produced at the instant at which the semiconductor switch Q 1 is made turned-off and for making the operation of the D flip-flop circuit 28 wait until the voltage at the current detecting terminal IS sufficiently increases.
  • the semiconductor switch Q 1 In a period in which the semiconductor switch Q 1 is made turned-off, at a time after a specified time from the timing at which the semiconductor switch Q 1 is made turned-off, the voltage at the current detecting terminal IS exceeding the threshold voltage, set by the voltage source VP 2 , makes the operation mode switched to a B mode.
  • the output terminal Q of the D flip-flop circuit 28 In the B mode, the output terminal Q of the D flip-flop circuit 28 outputs an H level signal.
  • the inverter 30 inverts the inputted H level signal to an L level signal to control the switch SW 1 so as to become in an opened state.
  • the H level signal as the output of the D flip-flop circuit 28 is directly given to control the switch SW 2 so as to become in a closed state. This is to allow the voltage of the voltage source VP 4 to be supplied to the current comparator 27 as an overcurrent limiting threshold voltage.
  • the voltage at the current detecting terminal IS from the state of being raised during the period during which the semiconductor switch Q 1 was made turned-off, drops down to a voltage close to zero volt simultaneously with the turning-on of the semiconductor switch Q 1 .
  • an error signal such as a noise.
  • the one-shot circuit 23 continuously inputting set signals to the set terminal S of the RS flip-flop circuit 24 for a specified length of time (for example, the minimum turned-on width set at several hundreds of nanoseconds) when the valley detecting unit 22 detects a voltage that is to turn-on the semiconductor switch Q 1 .
  • the semiconductor switch Q 1 is not made turned-off for the specified length of time from the time of being made turned-on, by which a faulty operation can be prevented that causes the semiconductor switch Q 1 to be turned-off by a noise immediately after the semiconductor switch Q 1 is made turned-on.
  • the switching power supply system is brought into a stand-by mode.
  • an overcurrent limiting threshold voltage is lowered (set to the condition under which the voltage of the voltage source VP 3 >the voltage of the voltage source VP 4 ) so that an overcurrent limitation can be imposed with a load lighter than an ordinary load.
  • the stand-by mode it is required to lower excessive power consumption for the reduction of stand-by power consumption.
  • the light-emitting side photocoupler element PC 2 e and the photo-detecting side photocoupler element PC 2 r are made turned-off to enable reduction in excessive power consumption by an amount consumed therein.
  • FIG. 3 is a circuit diagram showing an example of a configuration of a circuit of a switching power supply system according to a second embodiment of the invention.
  • the switching power supply system according to the second embodiment compared with the switching power supply system according to the first embodiment, is different from the first embodiment in the way of detecting the turning-off of the semiconductor switch Q 1 .
  • a control IC 40 in the switching power supply system according to the second embodiment an inverting output terminal Q of the RS flip-flop circuit 24 and the timer 21 are connected. This allows the timer 21 to start its operation on receiving a turning-off control signal whose level becomes an H level at the turning-off of the semiconductor switch Q 1 , to output a pulse signal after a specified length of time has passed and to supply the outputted pulse signal to the clock input terminal CK of the D flip-flop circuit 28 .
  • control IC 40 is the same as that of the control IC 10 in the first embodiment and the configuration of the switching power supply system other than the control IC 40 is also the same as that of the first embodiment. Therefore, the operations of the control IC 40 and the switching power supply system using the control IC 40 are the same as those of the first embodiment. Therefore, detailed explanations thereof will be omitted here.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Dc-Dc Converters (AREA)
US13/178,909 2010-07-08 2011-07-08 Semiconductor integrated circuit and switching power supply system Active 2032-07-05 US8625309B2 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2010155974A JP5488274B2 (ja) 2010-07-08 2010-07-08 半導体集積回路およびスイッチング電源装置
JP2010-155974 2010-07-08

Publications (2)

Publication Number Publication Date
US20120008346A1 US20120008346A1 (en) 2012-01-12
US8625309B2 true US8625309B2 (en) 2014-01-07

Family

ID=45438444

Family Applications (1)

Application Number Title Priority Date Filing Date
US13/178,909 Active 2032-07-05 US8625309B2 (en) 2010-07-08 2011-07-08 Semiconductor integrated circuit and switching power supply system

Country Status (2)

Country Link
US (1) US8625309B2 (ja)
JP (1) JP5488274B2 (ja)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20120287682A1 (en) * 2011-05-10 2012-11-15 Chengdu Monolithic Power Systems Co., Ltd. Switch mode power supply and control method thereof
US20130300384A1 (en) * 2012-05-08 2013-11-14 Chengdu Monolithic Power Systems Co., Ltd. Isolated switching mode power supply and the method thereof
US20140071715A1 (en) * 2012-09-11 2014-03-13 Rohm Co., Ltd. Dc/dc converter, control circuit and control method thereof, power supply, power adapter and electronic apparatus using the same
US9742292B2 (en) * 2015-10-22 2017-08-22 Inno-Tech Co., Ltd. Multifunction power conversion device

Families Citing this family (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102011104441A1 (de) * 2011-06-16 2012-12-20 Fujitsu Technology Solutions Intellectual Property Gmbh Schaltnetzteil, Betriebsverfahren und Verwendung eines Schaltnetzteils in einem Computer
CN103094884B (zh) * 2011-11-08 2014-07-30 昂宝电子（上海）有限公司 保护开路和/或短路状况下的电源变换系统的系统和方法
JP5857680B2 (ja) * 2011-11-28 2016-02-10 株式会社デンソー 位相補償回路および半導体集積回路
JP5857702B2 (ja) * 2011-12-12 2016-02-10 富士電機株式会社 スイッチング電源装置
JP6083668B2 (ja) * 2012-01-11 2017-02-22 パナソニックＩｐマネジメント株式会社 スイッチング電源回路
US9356525B2 (en) 2012-08-31 2016-05-31 Canon Kabushiki Kaisha Power supply device and image forming apparatus
US9036369B2 (en) * 2012-10-12 2015-05-19 Power Integrations, Inc. Programming of an integrated circuit on a multi-function terminal
TWI481181B (zh) * 2012-12-28 2015-04-11 Ind Tech Res Inst 直流轉交流電力轉換裝置及其方法
US9276481B2 (en) * 2013-09-18 2016-03-01 Inno-Tech Co., Ltd. Power control device for dynamically adjusting frequency
JP6220249B2 (ja) 2013-12-02 2017-10-25 ローム株式会社 スイッチングコンバータおよびその制御回路、ａｃ／ｄｃコンバータ、電源アダプタおよび電子機器
JP6320210B2 (ja) * 2014-07-15 2018-05-09 Fdk株式会社 電源装置
WO2017069785A1 (en) * 2015-10-23 2017-04-27 Dialog Semiconductor Inc. Primary side regulated flyback converter with calibrated output voltage
JP6788962B2 (ja) * 2015-11-19 2020-11-25 セイコーエプソン株式会社 診断回路、電子回路、電子機器および移動体
CN105846653B (zh) * 2016-04-28 2018-06-22 成都芯源系统有限公司 开关变换电路及其控制电路和方法

Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6061257A (en) * 1998-09-28 2000-05-09 Stmicroelectronics S.R.L. Wholly integrated protection from the effects of a short circuit of the output of a flyback converter
JP2002136124A (ja) 2000-10-27 2002-05-10 Shindengen Electric Mfg Co Ltd フライバック型スイッチング電源
US7061225B2 (en) * 2004-06-29 2006-06-13 System General Corp. Apparatus and method thereof for measuring output current from primary side of power converter
JP2007014082A (ja) 2005-06-29 2007-01-18 Sharp Corp スイッチング電源回路及びそれを用いた電子機器
US20070046294A1 (en) 2005-08-26 2007-03-01 Matthews David M H Method and apparatus to select a parameter/mode based on a time measurement
JP2007258294A (ja) 2006-03-22 2007-10-04 Fuji Electric Device Technology Co Ltd 半導体集積回路
US7339359B2 (en) 2005-03-18 2008-03-04 Fairchild Semiconductor Corporation Terminal for multiple functions in a power supply
US7764521B2 (en) * 2007-05-11 2010-07-27 Richtek Technology Corp. Apparatus and method for providing multiple functions and protections for a power converter
US7859862B2 (en) * 2007-09-17 2010-12-28 Richtek Technology Corp. Apparatus and method for regulating constant output voltage and current on primary side in a flyback converter
US8199533B2 (en) * 2008-08-26 2012-06-12 Sanken Electric Co., Ltd. Switching power supply device

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002247850A (ja) * 2001-02-15 2002-08-30 Kaga Component Kk スイッチング電源装置
JP2005278376A (ja) * 2004-03-26 2005-10-06 Shindengen Electric Mfg Co Ltd スイッチング電源装置

Patent Citations (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6061257A (en) * 1998-09-28 2000-05-09 Stmicroelectronics S.R.L. Wholly integrated protection from the effects of a short circuit of the output of a flyback converter
JP2002136124A (ja) 2000-10-27 2002-05-10 Shindengen Electric Mfg Co Ltd フライバック型スイッチング電源
US7061225B2 (en) * 2004-06-29 2006-06-13 System General Corp. Apparatus and method thereof for measuring output current from primary side of power converter
US7339359B2 (en) 2005-03-18 2008-03-04 Fairchild Semiconductor Corporation Terminal for multiple functions in a power supply
JP2008533972A (ja) 2005-03-18 2008-08-21 フェアーチャイルド セミコンダクター コーポレイション 電源における複数の機能のための端子
JP2007014082A (ja) 2005-06-29 2007-01-18 Sharp Corp スイッチング電源回路及びそれを用いた電子機器
US20070046294A1 (en) 2005-08-26 2007-03-01 Matthews David M H Method and apparatus to select a parameter/mode based on a time measurement
JP2007073954A (ja) 2005-08-26 2007-03-22 Power Integrations Inc 時間計測に基づきパラメータ／モードを選択する方法及び装置
JP2007258294A (ja) 2006-03-22 2007-10-04 Fuji Electric Device Technology Co Ltd 半導体集積回路
US7764521B2 (en) * 2007-05-11 2010-07-27 Richtek Technology Corp. Apparatus and method for providing multiple functions and protections for a power converter
US7859862B2 (en) * 2007-09-17 2010-12-28 Richtek Technology Corp. Apparatus and method for regulating constant output voltage and current on primary side in a flyback converter
US8199533B2 (en) * 2008-08-26 2012-06-12 Sanken Electric Co., Ltd. Switching power supply device

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20120287682A1 (en) * 2011-05-10 2012-11-15 Chengdu Monolithic Power Systems Co., Ltd. Switch mode power supply and control method thereof
US8891258B2 (en) * 2011-05-10 2014-11-18 Monolithic Power Systems, Inc Switch mode power supply and control method thereof
US20130300384A1 (en) * 2012-05-08 2013-11-14 Chengdu Monolithic Power Systems Co., Ltd. Isolated switching mode power supply and the method thereof
US9065348B2 (en) * 2012-05-08 2015-06-23 Chengdu Monolithic Power Systems Co., Ltd. Isolated switching mode power supply and the method thereof
US20140071715A1 (en) * 2012-09-11 2014-03-13 Rohm Co., Ltd. Dc/dc converter, control circuit and control method thereof, power supply, power adapter and electronic apparatus using the same
US9190916B2 (en) * 2012-09-11 2015-11-17 Rohm Co., Ltd. DC/DC converter, control circuit and control method thereof, power supply, power adapter and electronic apparatus using the same
US9742292B2 (en) * 2015-10-22 2017-08-22 Inno-Tech Co., Ltd. Multifunction power conversion device

Also Published As

Publication number Publication date
JP5488274B2 (ja) 2014-05-14
US20120008346A1 (en) 2012-01-12
JP2012019632A (ja) 2012-01-26

Similar Documents

Publication Publication Date Title
US8625309B2 (en) Semiconductor integrated circuit and switching power supply system
US10075081B2 (en) Insulated synchronous rectification DC/DC converter
US10218283B2 (en) Insulated synchronous rectification DC/DC converter
US9177508B2 (en) Light emitting apparatus
US8531163B2 (en) Switching power supply device, integrated circuit, and switching power supply device operation condition setting method
US7492615B2 (en) Switching power supply
US8482943B2 (en) Power transistor driving circuits and methods for switching mode power supplies
US7928713B2 (en) Method and apparatus for synchronous buck with active negative current modulation
US8295062B2 (en) Switching power supply apparatus and semiconductor device
KR20190025493A (ko) 전원 제어용 반도체 장치, 전원 장치 및 ｘ 콘덴서의 방전 방법
CN108880296B (zh) 电源转换系统
EP2175550B1 (en) Ultra-low-power power conversion controller and associated method
US8922138B2 (en) Control circuit for light emitting apparatus
US8294494B2 (en) Triangular-wave generating circuit synchronized with an external circuit
KR20080088006A (ko) 스위칭 모드 파워 서플라이 및 그 구동 방법
US9742299B2 (en) Insulated synchronous rectification DC/DC converter
US5631810A (en) Control of switching devices in synchronized-rectification system
US8699241B2 (en) Switching mode power supply
US9754740B2 (en) Switching control circuit and switching power-supply device
CN112217399A (zh) 开关型调节驱动器及其调节驱动方法
US20120044724A1 (en) Switching power supply apparatus
US8830706B2 (en) Soft-start circuit
KR101431143B1 (ko) 전력 변환기, 그 스위칭 제어 장치 및 구동 방법
TWI551022B (zh) Dynamic drive capability adjustment of the power control device
US20120008343A1 (en) High-Voltage Startup Method and Power Management Apparatus

Legal Events

Date Code Title Description
AS Assignment

Owner name: FUJI ELECTRIC CO., LTD., JAPAN

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:KAWAMURA, KAZUHIRO;REEL/FRAME:026942/0715

Effective date: 20110823

STCF Information on status: patent grant

Free format text: PATENTED CASE

FPAY Fee payment

Year of fee payment: 4

MAFP Maintenance fee payment

Free format text: PAYMENT OF MAINTENANCE FEE, 8TH YEAR, LARGE ENTITY (ORIGINAL EVENT CODE: M1552); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY

Year of fee payment: 8